Lighting systems for luminous advertising panels, way signs, traffic marks, furnishing elements etc. are widely spread in connection with visual communication development which shall be effective even during evening and night hours and in zones not exposed to day light.
There are plentiful examples of these lighting systems.
Some known systems are located on the outsides of the signs to be illuminated so that the signs or indications are visible by reflected light.
For example, internally lighted signs are also known, usually formed by neon lamps mounted inside a container provided with an opaline plate bearing on its surface the indications or signs which are usually in transparent and coloured material.
These internally or externally illumination of marks and signs achieved with normal neon lamps shall , however, be directly powered from the mains because of their high consumption rate.
To remedy this drawback of the lighting system, it is sometimes possible to replace the neon lamps of internal lighting systems by LEDs (light emitting diodes). These LEDs are fitted inside the container where they are forming the required signs or words with the utilization of rays of light emitted b the LEDs positioned side by side so as to form the word or image.
These led""s have a high brilliancy, low electric energy consumption and a long average life of about one hundred thousand hours. Panels are known that are completely covered by led""s which are energized in different modes so as to form different images or words. In these applications, the opaline plate may be replaced by a transparent plate.
This led application system offers a considerable economic advantage, especially regarding consumption with the possibility for the human eye to read at a distance of about 150 m.
This led lighting system has, in turn, the serious drawback in that it requires a great number of led""s, emittingxe2x80x94as is knownxe2x80x94a rather concentrated light; furthermore the already known led systems permit to form a specific image and to change this image it will be necessary to change the arrangement of the led""s inside the container or will require at least a great number of led""s to be energized in different ways.
This invention has the aim to obtain a luminous diffused light panel characterized by low energy consumption and limited thickness, requiring only a limited number of led""s.
According to this invention, the luminous panel consists of a plate assembly and accessories implemented as follows.
The first plate consists of transparent material, for instance metacrylate, polycarbonate, glass, crystal or any other light conducting material, provided along one, two or more of its edges with a linear led assembly mounted on a suitable support and sequence energized.
This support may be a printed circuit and a reflecting element, further securing the perfect positioning of the led""s, is inserted between the support and the polished edge of the plate.
The back side of this first transparent plate is prepared to reflect and diffuse the led emitted light by covering this surface with a white paint coat or with a glued or adhesive film of suitable thickness and material. This first plate is usually flat but it may also be curved. In this way, the light of the led""s propagates through the light conducting plate and reflects on the paint or film, coating its back surface, thus diffusing the light outwards.
A second opaline plate, placed at a few millimeters from the first transparent plate, will further diffuse the light from its surface at an extraordinary high emission uniformity. The latter plate may be replaced by two plates having a lower opacity grade but which will be positioned nearer to the first plate so as further to reduce the thichness of the luminous panel.
A third protective plate in transparent material will be placed in front of the second plate at a few millimeter distance or will be resting on the second plate, while another protective plate, which needs not be transparent, may be placed behind the first plate.
The luminous panel thus described will diffuse the light only from the second opaline plate surface. The case is also considered in which a luminous panel diffuses the light from both sides. In such case, the white paint or film is applied in alternating and staggered strips or with other schemes on both surfaces of the first light conducting plate thus causing the light to be reflected and diffused from both sides of the first plate. The luminous panel is then equipped with two (or four) opaline plates, one on each side and also with two transparent protective plates one on each side. The plate and led assembly together with their supports are mounted in a structure of aluminium sections or in other plastic material fitted on the four sides of the plates, which will thus form a peripheral frame, the corners of which are finished with corner caps screwed onto the sections. If required, proper electronic components will be provided for grounding and protection of the luminous panel against overvoltage and electrostatic discharge.
The peculiar arrangement of the led""s, the special plate sequence and the particular aluminium or plastic sections will permit to reduce the panel thickness to about 50 mm against the 130 mm thickness of known panels internally lighted by neon lamps.
Such luminous diffused light panels of limited thickness and low consumption rate, preferably equipped with two series of lateral led""s, will be able, for instance, to illuminate an advertising sign at low energy consumption. It is also suitable to illuminate identification panels of any kind, such as traffic signs, radiograph reading devices as well as luminous panels for furnishings, consoles and luminous surfaces.
The notices or indications to be highlighted may be printed or serigraphed on the outer surface of the opaline plate or on the internal surface of the transparent protection plate or on a translucid film inserted between the two above mentioned plates.
As by a first solution as explained, the supporting and the reflecting clement of the Led""s are mutually independent and are kept in place by properly shaped framing sections.
This arrangement is practical for panels of limited size, while for large sized panels, the alignment of the supporting sections, the reflecting elements and therefore of the Led""s may sometimes be difficult.
This drawback is eliminated, according to this new invention, by manufacturing the supporting structure, consisting of the printed circuit, and the reflecting element so that they can be assembled before they are fitted into the section frame which is modified in order to permanently lodge the above mentioned supporting structure and the reflecting element.
According to the above description the first transparent plate surrounded by the leds has one surface covered with a white paint coat or with a glued or adhesive film diffusing the light which propagates through the other, non-coated surface of the plate.
In some cases, especially for large sized panels, the light intensity at the centre of the panels i.e. further away from the peripheral led""s, may be lower due to the fact that the light is mainly diffused in the peripheral zones and is attenuated in the central zones. In these cases light diffusion can be much improved, according this invention, if the surface of the first transparent plate generating diffused light on one side only is treated, instead of being uniformly coated with paint or a film, so as to create a geometrical pattern on this surface determined by alternating areas reflecting the light to the opposite panel surface and non-treated areas allowing the light to propagate through the plate. The light intensity in the centre of the plate will thus be improved and light diffusion through the whole plate surface will become more uniform.
The reflecting surface areas may be obtained by the application of materials such as paints, serigraphy inks, transparent or opaque adhesive films or even by chemical etching using solutions reacting with the plate surface, or by chipping or roughing processes or sand blasting or in the case of plates in plastic material, by thermal deformation.
For exemplification purposes, ink deposited by serigraphy on suitably spaced parallel strips of a few millimeter width will yield excellent results.
However the pattern may be widely varying: it may be linear (lengthwise, transverse or diagonally with respect to the light emitted by the led""s), chequered, spiral formed or differently dimensioned so as to create a nuanced light diffusion.
An additional advantage of this method regarding treated and non-treated areas is that the second opaline plate, used to obtain a better light diffusion, may be placed nearer to the light emitting side of the first transparent plate which is surrounded by led""s, without generating halations or less luminous areas. This is an obvious improvement with respect to the above mentioned solution.
As for lighting panels in which the light is diffused from both sides, the process selected from those indicated above has to be alternatively performed on both sides of the first transparent plate, obviously in alternate pattern: for example, the serigraphed stripes on one side shall be matched by a non treated area and shall therefore be transparent on the other side.
The invention in question is illustrated in its exemplar solutions in the closed drawings in which: